Conventionally, a laminated piezoelectric actuator which is formed by laminating a piezoelectric element has been commonly used in the drive units of linear actuators and valves. A flow control device for controlling flow rate with a piezoelectric driving valve using a laminated piezoelectric actuator is also known.
The flow control device shown in FIG. 10 presents an example of this type of flow control device. It opens and closes the valve element 13, which is made with, for example, a metal diaphragm, interposed with flow passage 11 inside the valve block 12 by using the laminated piezoelectric actuator 2 attached to the valve block 12. (Patent document 1-3)
The flow control device shown in FIG. 10 is referred to as a pressure type flow control device. When the so-called critical expansion condition (P1/P2)>=approx. 2 is maintained between the downstream pressure P2 of the orifice 14 interposed by the flow passage 11 and upstream pressure P1, the relationship of gas flow rate Q flowing through the orifice 14 becomes Q=KP1 (where K is a constant).
Applying this relationship, the flow rate Q can be controlled with high accuracy by controlling the pressure P1 detected by the pressure detector 15. Moreover, the flow rate hardly fluctuates even when the upstream gas pressure of valve 13 changes dramatically. High precision in the pressure P1 is achieved by the high response of the laminated piezoelectric actuator 2.